If you can make a *constant current* load, then it's as simple as graphing voltage over time, and probably adding a low-voltage cutoff at the appropriate voltage. If you take the measurements at a regular interval, then you can also apply math to come up with a reasonable version of power in addition to load. Lots of voltmeters have PC based loggers.
The advantages of all of the loads I linked to are that they're well designed constant current loads. As to the advanced software from West Mountain radio, that probably isn't needed. What I was referring to was the $1K per 1000 watts of load cell once you get above 150W, but compared to a brand new dc load at those same wattages it isn't all that pricey. On Thu, Sep 19, 2019 at 8:03 PM Chuck McCown <ch...@wbmfg.com> wrote: > I can make the loads. I like Mtn west but they want too much for the > advanced version of the software. > > Sent from my iPhone > > On Sep 19, 2019, at 6:01 PM, Forrest Christian (List Account) < > li...@packetflux.com> wrote: > > The west mountain radio CBA IV can't really be beat for price and > functionality. > > For around $200, you get a little USB-attached unit which can discharge up > to the lower of 150W or 40A, at a constant current. So you can set the > discharge to the 20 hour rate for a battery, and an app on the PC will > will log and graph. For newer batteries, this almost always matches > pretty well with the datasheet voltage. I use this fairly regularly to > verify the smaller batteries I have around. If you stick with the 20 hour > rate @ 12V, you're good up to around 250AH (250AH at the 20hour rate = > 12.5A/150W). > > If you're looking at an entire array you're probably going to need more > power - they have add on 'amplifiers' but they aren't cheap. Another > option is to go get a real DC load with appropriate software. See > https://www.youtube.com/watch?v=8y7mFXD8wII for an example. The rigol > illustrated is good up to 350W, other manufacturers have pretty much any > size you want, if you can afford it. There are also usually a few > floating around ebay of older types, if you can find or write suitable > software (i.e. write a python script to pull the data out at regular > intervals). > > On Thu, Sep 19, 2019 at 7:32 AM Chuck McCown <ch...@wbmfg.com> wrote: > >> Discharge and logging. >> >> Sent from my iPhone >> >> On Sep 18, 2019, at 7:12 PM, Forrest Christian (List Account) < >> li...@packetflux.com> wrote: >> >> Are you talking about doing a discharge test on a battery and logging >> it? (Aka West Mountain Radio CBA IV, or the output from any of several DC >> loads w/data ports) >> >> Or are you looking for current in/out graphing over a long period of time >> on a system? This is pretty common and I *do* have solutions for this. >> >> Or battery state of charge measurement? A victron BMV-700 series, or a >> trimetric battery monitor /w some sort of logging? >> >> Or...? >> >> Also, if this is monitoring a live system, what are you charging it with >> and does it have a data port on it? >> >> On Tue, Sep 17, 2019 at 7:35 AM Chuck McCown <ch...@wbmfg.com> wrote: >> >>> Just graphical discharge records. >>> >>> Sent from my iPhone >>> >>> On Sep 17, 2019, at 4:33 AM, Forrest Christian (List Account) < >>> li...@packetflux.com> wrote: >>> >>> Nope, never got around to it. >>> >>> I've recently become aware of several products which do something >>> similar to what I had in mind. What were you looking for? >>> >>> >>> >>> On Mon, Sep 16, 2019 at 5:09 PM Chuck McCown <ch...@wbmfg.com> wrote: >>> >>>> Did you ever build that battery tester characterizer thingy? >>>> -- >>>> AF mailing list >>>> AF@af.afmug.com >>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>> >>> >>> >>> -- >>> - Forrest >>> >>> -- >>> AF mailing list >>> AF@af.afmug.com >>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>> >>> -- >>> AF mailing list >>> AF@af.afmug.com >>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>> >> >> >> -- >> - Forrest >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> > > > -- > - Forrest > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- - Forrest
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